Normal blood coagulation is a complex physiological and biochemical process that is regulated at several levels. The process of blood coagulation involves activation of a coagulation factor cascade leading to fibrin formation and platelet aggregation along with local vasoconstriction (reviewed by Davie et al., Biochemistry 30:10363, 1991). The clotting cascade is composed of an “extrinsic” pathway thought to be the primary means of normal coagulation initiation and an “intrinsic” pathway contributing to an expanded coagulation response. The normal response to a bleeding insult involves activation of the extrinsic pathway. Activation of the extrinsic pathway is initiated when blood comes in contact with tissue factor (TF), a cofactor for factor VII that becomes exposed or expressed on tissues following insult. TF forms a complex with FVII that facilitates the production of FVIIa. FVIIa then associates with TF to convert FX to the serine protease FXa, which is a critical component of the prothrombinase complex. The conversion of prothrombin to thrombin by the FXa/FVa/calcium/phospholipid complex stimulates the formation of fibrin and activation of platelets, all of which is essential to normal blood clotting. Normal hemostasis is further enhanced by intrinsic pathway factors IXa and VIIIa, which also convert FX to FXa. See also Weitz, J. I., et al., Chest, 126 (3). September 2004 (Suppl), 265 S.
Sulfated polysaccharides are a class of molecules characterized by a plethora of biological activities with often favorable tolerability profiles in animals and humans. These polyanionic molecules are often derived from plant and animal tissues and encompass a broad range of subclasses including heparins, glycosaminoglycans, fucoidans, carrageenans, pentosan polysulfates, and dermatan or dextran sulfates. Heparin-like sulfated polysaccharides exhibit differential anticoagulant activity mediated through antithrombin III and/or heparin cofactor II interactions (Toida T C, Linhardt, R J., Trends in Glycoscience and Glycotechnology 2003; 15:29-46).
While one such sulfated polysaccharide, oral heparin, has been considered for development as an anticoagulant (A Dunn, Idrugs, 3:817-824, 2000), heparin is inadequate because of its serious complications which include intraoperative and postoperative bleeding, osteoporosis, alopecia, heparin resistance, heparin rebound, heparin-induced thrombocytopenia (HIT), heparin-induced thrombocytopenia thrombosis syndrome (HITTS), and other disadvantages including multiple days for anticoagulation to attenuate after discontinuing the drug (Iqbal O, et al, Fareed J, Expert Opin Emerg Drugs 6:111-135, 2001; Roberts, H R, Anesthesiology 100:722-730, 2004). Heparin is conventionally administered parenterally, and possesses an oral uptake level of only about 1% (Fitton, J. H., Glycoscience, The Nutrition Science Site, modified Jan. 1, 2005).
In contrast to heparin, another sulfated polysaccharide, fucoidan, a sulfated polysaccharide isolated from sea algae, has been shown to regulate (i.e., promote) coagulation (U.S. Patent Publication No. 2005/0282771). Specifically, fucoidans, when administered at low concentrations in vitro, or low subcutaneous doses in vivo, provide improved (accelerated) clotting in hemophilic settings through extrinsic pathway activation (Liu, T., et al., and Johnson, K. W., Thrombosis and Haemostasis, 95:68-76, 2006), demonstrating a pro-coagulant activity. At higher doses fucoidan can have an anticoagulant effect similar to heparin. In light of the problems associated with current anticoagulants like heparin or warfarin, there clearly remains a need for agents, such as fucoidan, that can overcome one or more of the problems associated with currently available anticoagulant therapy.
Thus, there remains a need for an improved method to cost-effectively and efficiently produce fucoidan enriched extract with optimal activity for procoagulant or anticoagulant therapeutic use.